The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis
<p>The calcium sensing receptor (CaSR), a G-protein coupled receptor (GPCR), and its downstream signalling pathways are essential for calcium homeostasis. Loss- or gain-of-function (LOF and GOF, respectively) mutations in components of these pathways result in disorders of calcium homeostasis...
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| Materialtyp: | Lärdomsprov |
| Språk: | English |
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2016
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| _version_ | 1826279253343207424 |
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| author | Rogers, A |
| author2 | Thakker, R |
| author_facet | Thakker, R Rogers, A |
| author_sort | Rogers, A |
| collection | OXFORD |
| description | <p>The calcium sensing receptor (CaSR), a G-protein coupled receptor (GPCR), and its downstream signalling pathways are essential for calcium homeostasis. Loss- or gain-of-function (LOF and GOF, respectively) mutations in components of these pathways result in disorders of calcium homeostasis including Familial hypocalciuric hypercalcaemia (FHH) and Autosomal dominant hypocalcaemia (ADH). FHH type 3 (FHH3) is due to LOF mutations in the σ2 subunit (AP2σ2) of adaptor protein-2 (AP-2). The FHH3-associated AP2σ2 mutations identified to date affect the Arg15 residue and comprise heterozygous Arg15Cys, Arg15Leu, and Arg15His mutations. AP-2 is a ubiquitously expressed heterotetrameric protein, with a central role in clathrin-mediated endocytosis of transmembrane proteins, such as GPCRs.</p> <p>This thesis demonstrates that AP2σ2 mutations account for &Tilde;7% of all FHH mutations, only affect the Arg15 residue and show evidence of mutation bias, with only AP2σ2 Arg15Cys, Arg15Leu, and Arg15His mutations identified. Additionally, the study has identified <em>de novo</em> AP2σ2 mutations and revealed that FHH3 probands may present with a broader phenotype not seen in FHH1. The heterozygous missense AP2σ2 mutation was demonstrated to have no effect on the stability of the AP-2 complex in vivo. This thesis revealed that gain-of-function AP2σ2 mutations are unlikely to be a cause of ADH, which is due to GOF mutations in CaSR in &GT;70% of cases.</p> <p>The CaSR activates its downstream signalling pathways, including the mitogen-activated protein kinase (MAPK) pathway, through coupling with its associated G-proteins. The AP2σ2 mutations resulted in loss of activating phosphorylation events in the MAPK pathway suggesting a role for AP2σ2 in CaSR signalling. Additionally, the AP2σ2 Arg15Cys, Arg15His and Arg15Leu mutations were revealed to exert differential effects on the Gα<sub>q/11</sub> and MAPK signalling pathways, suggesting mutation-bias signalling.</p> <p>Clathrin-mediated endocytosis is crucial for embryological development. This thesis has demonstrated that mice homozygous for an <em>Ap2s1</em> splice site mutation, predicted to produce a functional knock-out, were lethal before embryonic day 12.5 (E12.5), suggesting AP2σ2 is essential for cell viability in the developing embryo.</p> <p>Thus, the work of this thesis has further elucidated the role of AP2σ2 in the biological pathways of CaSR signalling and clathrin-mediated endocytosis, and in the molecular pathology of disorders of calcium homeostasis.</p> |
| first_indexed | 2024-03-06T23:55:59Z |
| format | Thesis |
| id | oxford-uuid:743b6eb9-ddcd-46bd-aee0-78ff4b8b6b2c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:55:59Z |
| publishDate | 2016 |
| record_format | dspace |
| spelling | oxford-uuid:743b6eb9-ddcd-46bd-aee0-78ff4b8b6b2c2022-03-26T20:01:29ZThe role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasisThesishttp://purl.org/coar/resource_type/c_db06uuid:743b6eb9-ddcd-46bd-aee0-78ff4b8b6b2cCalcium in the bodyG proteins--ReceptorsEnglishORA Deposit2016Rogers, AThakker, RCox, R<p>The calcium sensing receptor (CaSR), a G-protein coupled receptor (GPCR), and its downstream signalling pathways are essential for calcium homeostasis. Loss- or gain-of-function (LOF and GOF, respectively) mutations in components of these pathways result in disorders of calcium homeostasis including Familial hypocalciuric hypercalcaemia (FHH) and Autosomal dominant hypocalcaemia (ADH). FHH type 3 (FHH3) is due to LOF mutations in the σ2 subunit (AP2σ2) of adaptor protein-2 (AP-2). The FHH3-associated AP2σ2 mutations identified to date affect the Arg15 residue and comprise heterozygous Arg15Cys, Arg15Leu, and Arg15His mutations. AP-2 is a ubiquitously expressed heterotetrameric protein, with a central role in clathrin-mediated endocytosis of transmembrane proteins, such as GPCRs.</p> <p>This thesis demonstrates that AP2σ2 mutations account for &Tilde;7% of all FHH mutations, only affect the Arg15 residue and show evidence of mutation bias, with only AP2σ2 Arg15Cys, Arg15Leu, and Arg15His mutations identified. Additionally, the study has identified <em>de novo</em> AP2σ2 mutations and revealed that FHH3 probands may present with a broader phenotype not seen in FHH1. The heterozygous missense AP2σ2 mutation was demonstrated to have no effect on the stability of the AP-2 complex in vivo. This thesis revealed that gain-of-function AP2σ2 mutations are unlikely to be a cause of ADH, which is due to GOF mutations in CaSR in &GT;70% of cases.</p> <p>The CaSR activates its downstream signalling pathways, including the mitogen-activated protein kinase (MAPK) pathway, through coupling with its associated G-proteins. The AP2σ2 mutations resulted in loss of activating phosphorylation events in the MAPK pathway suggesting a role for AP2σ2 in CaSR signalling. Additionally, the AP2σ2 Arg15Cys, Arg15His and Arg15Leu mutations were revealed to exert differential effects on the Gα<sub>q/11</sub> and MAPK signalling pathways, suggesting mutation-bias signalling.</p> <p>Clathrin-mediated endocytosis is crucial for embryological development. This thesis has demonstrated that mice homozygous for an <em>Ap2s1</em> splice site mutation, predicted to produce a functional knock-out, were lethal before embryonic day 12.5 (E12.5), suggesting AP2σ2 is essential for cell viability in the developing embryo.</p> <p>Thus, the work of this thesis has further elucidated the role of AP2σ2 in the biological pathways of CaSR signalling and clathrin-mediated endocytosis, and in the molecular pathology of disorders of calcium homeostasis.</p> |
| spellingShingle | Calcium in the body G proteins--Receptors Rogers, A The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title | The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title_full | The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title_fullStr | The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title_full_unstemmed | The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title_short | The role of the sigma subunit of Adaptor Protein-2, AP2σ2, in the regulation of calcium homeostasis |
| title_sort | role of the sigma subunit of adaptor protein 2 ap2σ2 in the regulation of calcium homeostasis |
| topic | Calcium in the body G proteins--Receptors |
| work_keys_str_mv | AT rogersa theroleofthesigmasubunitofadaptorprotein2ap2s2intheregulationofcalciumhomeostasis AT rogersa roleofthesigmasubunitofadaptorprotein2ap2s2intheregulationofcalciumhomeostasis |